Liquefaction of lignocellulose: bio-crude, char and chemistry of liquefaction

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(2) LIQUEFACTION OF LIGNOCELLULOSE BIO-CRUDE, CHAR AND CHEMISTRY OF LIQUEFACTION.

(3) Promotion committee: Chairman:. Prof. dr. ir. J.W.M. Hilgenkamp. University of Twente. Promotors:. Prof. dr. S.R.A. Kersten. University of Twente. Prof. dr. J.P. Lange. University of Twente. Assistant promotor:. Dr. ir. G. van Rossum. Shell, The Netherlands. Members:. Prof. dr. ir. L. Lefferts. University of Twente. Prof. dr. ir. J. Huskens. University of Twente. Prof. dr. ir. W. Prins. University of Gent. prof. dr. ir. B.M. Weckhuysen. University of Utrecht. The research described in this thesis was financially supported by Shell Global Solutions, Amsterdam, The Netherlands.. Liquefaction of lignocellulose: Bio-crude, char and chemistry of liquefaction Cover design: Maria Castellví Barnés ISBN: 978-90-365-4133-6 DOI-number: 10.3990/1.9789036541336 URL: http://dx.doi.org/10.3990/1.9789036541336 Printed by Gildeprint – Enschede, The Netherlands © 2016 Maria Castellví Barnés, Enschede, The Netherlands.

(4) LIQUEFACTION OF LIGNOCELLULOSE BIO-CRUDE, CHAR AND CHEMISTRY OF LIQUEFACTION. DISSERTATION. to obtain the degree of doctor at the University of Twente, on the authority of the rector magnificus, Prof.dr. H. Brinksma, on account of the decision of the graduation committee, to be publicly defended on Friday 27th of May, 2016 at 12:45. by. Maria Castellví Barnés born on 17th of March, 1988 in Barcelona, Spain.

(5) This dissertation has been approved by: Prof. dr. S.R.A. Kersten (Promotor) Prof. dr. J.P. Lange. (Promotor). Dr. ir. G. van Rossum (Assistant. Promotor).

(6) To my family Per estar sempre al meu costat.

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(8) Contents 1. Chapter 1 Introduction. 15. Chapter 2 Reagents and experimental procedure. 39. Chapter 3 Solvent, process parameter and recycle oil screening. 55. Chapter 4 Bio-crude characterization based on GPC preparative fractionation. 83. Chapter 5 Chemistry of the Liquefaction of wood and its model components. 117 Chapter 6 Effect of the reaction medium during liquefaction of lignocellulose 139 Chapter 7 Summary, conclusions and recommendations 149 Samenvatting 153 Resum 157 List of symbols 159 List of publications 161 Supporting information 215 Acknowledgements.

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(10) Chapter 1 Introduction.

(11) 2. |. Chapter 1: Introduction.

(12) 1. Importance of bio-fuels The discovery of fossil fuels at the beginning of the industrial revolution, allowed a huge development of the human society [1, 2]. This development has favoured an increase in global population and quality of life, but has also caused major changes in the earth environment, such as an increase in greenhouse emissions (contributing to climate change), a decrease in bio-diversity and an imbalance of the phosphorous and nitrogen cycles (used as fertilizers) [1-4]. In the coming years, the growth in global population and prosperity, especially of developing countries (e.g. China or However, more sustainable energy sources are needed and, therefore, alternatives to fossil energy sources are being explored. Furthermore, the need to secure energy supply (currently controlled by a limited number of countries) and the economic development they would provide (especially in the rural areas) are strong motivations for governments around the world to support the development of these. Nowadays, a quarter of the world’s energy consumption is used for transportation [9, 10]. This sector is presently powered by liquid fuels because of their high energy densities and because they are easy to store and transport. Here, bio-fuels stand as a sustainable substitute for fossil fuels, as they are carbon-based and, therefore, fit in the carbon-based (fossil) fuel existing infrastructure. Furthermore, unlike other energies like solar or wind, bio-fuels can provide a continuous energy supply and have less dependence on geographical location [1, 6-8]. In 2010, bio-fuels (mainly ethanol and bio-diesel) provided less than 2.5 % of the total energy consumption used in the transport sector [7, 10]. However, according to the International Energy Agency (IEA), 26 % of the total transport fuel demand in 2050 could be provided by bio-fuels, with 90 % of those being second generation biofuels [11].. 3. |. alternatives to conventional energy sources [1, 6-8].. Chapter 1: Introduction. India), is expected to increase even further the world’s energy demand [1, 5, 6]..

(13) 2. From biomass to bio-fuel 2.1. Lignocellulosic biomass Biomass is considered a carbon-neutral renewable energy source. However, economic, social and environmental impacts have to be taken into account when selecting the appropriate biomass to produce bio-fuels. The first generation of bio-fuels was obtained from sugars, starches and vegetable and animal fats. However, those biomass sources compete with the food industry. To overcome this problem, second generation bio-fuels were developed. These fuels are obtained from lignocellulosic biomass, which can be obtained in large amounts, for example, from agricultural and forestry residues. However, to guarantee a low environmental impact, the production of lignocellulose should take into account the type of land used for its cultivation (co-production with food crops or use of. 4. |. degraded or abandoned lands instead of replacing forests or other plantations), the. Chapter 1: Introduction. nutrient balances (e.g. nitrogen and phosphate) or the water sources [7, 8, 12-14]. Lignocellulose is the fibrous material forming the essential part of the cell wall of plants. It is mainly composed of three types of polymer, namely cellulose (40-50 wt%), hemicellulose (15-35 wt%) and lignin (15-35 wt%), which are connected to each other, providing strength and resistance to the material. Other components such as starch, proteins, fats or mineral salts are also found in smaller amounts [1519]. Cellulose is a carbohydrate composed of glucose units arranged in linear chains. These linear chains are connected to each other by hydrogen bonds and organized in crystalline and amorphous regions. Generally, wood cellulose has a polymerization degree of 10000 and a molecular weight of 1 MDa..

(14) Hemicellulose is an amorphous carbohydrate composed of various sugar monomers (i.e. glucose, mannose and galactose) arranged into branched polymers. It has a polymerization degree of 200 and a molecular weight of approximately 30 kDa. Lignin is an aromatic polymer composed of propyl-phenol units attached to each other by ether or carbon-carbon linkages. It has a molecular weight up to 20 kDa, corresponding to a polymerization degree of approximately 120.. Compared to traditional (fossil) fuels, biomass has high oxygen and water content that decreases its combustion value. It has also a very low density, which is detrimental for its transportation and storage [7, 20]. Biomass is thus converted into a liquid product that has higher energy density and is easier to handle and store.. involving either thermochemical (liquefaction, pyrolysis, and gasification), chemical. |. (hydrolysis) or biological (fermentation) routes. Occasionally, biomass conversion is. 5. Numerous techniques can be used to convert biomass into a liquid product,. Chapter 1: Introduction. 2.2. Liquefaction. preceded by a pre-treatment to fractionate the biomass (e.g. sugar isolation before fermentation) or to debilitate and make the lignocellulose structure more accessible (e.g. mild hydrolysis or uncatalysed steam explosion) [6, 7, 19, 21]. In the current work we used liquefaction for the conversion of biomass into biocrude, as it presents several advantages over other thermochemical processes. For instance, liquefaction is generally performed at milder temperatures than pyrolysis or gasification [7, 19], and it leads to higher oil yields than fast pyrolysis (oil yield > 90 C% vs 50-55 C%) [22-28]. In addition, liquefaction can be performed with wet biomass. In fact, liquefaction is frequently performed in water (hydrothermal liquefaction) or in solvent mixtures containing water. Research on biomass liquefaction started in the early 1970s at the Pittsburg Energy Research Centre (PERC). After those first studies, a lot of liquefaction processes have.

(15) been developed using a wide range of conditions (e.g. temperature, liquefaction medium, sub- or super-critical conditions, use of catalyst or use of reactive gases). For more extensive information about liquefaction studies the reader can consult several publications reviewing the topic [17, 22, 29-32]. Despite all the research performed on liquefaction, the process has not yet reached a commercial state. The reasons are that liquefaction processes are generally performed under extreme process conditions and tend to present problems regarding high bio-crude viscosities, formation of solids or loss of light species in aqueous phases. Furthermore, the produced bio-crude still requires upgrading if it is to be used as high quality fuel. Thus, further research is required to develop a technologically and economically feasible liquefaction process. However, studies should not only focus on process optimization, but also on the understanding of the process and the effect that the liquefaction conditions have on the product distribution and the oil composition and. 6. |. quality.. Chapter 1: Introduction. Our study focuses on a direct liquefaction process that does not require biomass pretreatment and that yields a bio-crude that can be blended with fossil fuels and introduced into existing refinery units for its further upgrading. To have an economically feasible process, certain requirements were defined. Liquefaction must be operated at relatively mild conditions, namely liquefaction temperatures around 300°C and pressures lower than 60 bar. To maintain low pressures, use of reactive gases or liquefaction media with low boiling points must be avoided. The liquefaction medium should consist of a cheap solvent that does not need to be separated from the final product. This can include cheap refinery streams, or a fraction of the produced bio-crude. Finally, the use of catalysts should also be avoided to prevent contamination of the resulting bio-crude and maintain low process costs..

(16) 2.3. Bio-crude Despite presenting better fuel properties than the initial biomass, bio-crude still contains more oxygen and has higher molecular weight (Mw) than conventional fuels (Figure 1). This leads to lower energy content, low volatility, high viscosities, coking tendency, chemical instability (they tend to condense and polymerize with time) and corrosiveness. Furthermore, bio-crude has low solubility in hydrocarbons (important if it needs to be blended with fossil fuels) and is incompatible with some of the materials used in the existing fuel infrastructure [15, 19, 33]. Therefore, common techniques for bio-crude upgrading are hydrodeoxygenation and zeolite upgrading (catalytic cracking). Hydrodeoxygenation produces aliphatic and aromatic hydrocarbons via hydrogen addition and oxygen removal. Zeolite upgrading or catalytic cracking produces aromatics, light alkanes and coke via a number. of. reactions. including. dehydration,. cracking,. polymerization,. 7. |. deoxygenation, and aromatization [19, 33-35].. Chapter 1: Introduction. upgrading of the bio-crude is essential to obtain a high quality fuel. The most. 60. O content (wt%). 50. Lignocellulosic biomass. 40 Liquefaction 30. Bio-crude. 20 Upgrading 10 Crude oil Fuel. 0 10. 100. 1000. 10000. 100000. 1000000 10000000. Molecular weight (Da). Figure 1. Oxygen content and Mw of initial biomass, bio-crude and bio-fuel [39].. A good characterization of the bio-crude is essential to determine its quality and decide which treatment is required for its upgrading. Many techniques are used for.

(17) bio-crude characterization, such as gas chromatography (GC), two-dimensional GC (GCxGC), liquid chromatography (LC, including GPC), nuclear magnetic resonance (NMR), Fourier transformed infrared spectroscopy (FTIR) or high resolution mass spectrometry (HR-MS). Sometimes, sample preparation or pre-treatment (e.g. fractionation, extraction or distillation) is required to obtain more detailed information [36, 37]. However, some of these techniques suffer from practical limitations. For instance, gas chromatography can only detect the light components of the bio-crude [36, 38], or NMR and FTIR analyses may be obstructed if the biocrude is highly diluted in the liquefaction solvent.. 3. Scope and outline of the thesis The work presented in this thesis focuses on the characterization of the liquefaction products, the chemistry of the liquefaction process in terms of reactivity of biomass components, and the role of the liquefaction medium. This study was performed in. 8. |. parallel to the work of S. Kumar [29], which focused on the engineering and process. Chapter 1: Introduction. design of the liquefaction. In chapter 2, all reagents and materials, experimental procedures, characterization techniques and the product definitions are presented. In chapter 3, we present a fast screening of the effect of various process parameters (i.e. liquefaction solvent, temperature and time) on product distribution and oil quality. Experiments with recycling of the produced bio-crude as liquefaction medium are also shown. The results obtained in this chapter are used to define the research questions that will be addressed in the following chapters. The excess of liquefaction solvent in the final liquid product (> 90 wt%) prevented a proper characterization of the liquefaction bio-crude. Due the high boiling point of the liquefaction solvent and its similar chemical composition with the bio-crude, conventional fractionation techniques (e.g. distillation or solvent extraction) were not suitable for bio-crude isolation. In chapter 4 we develop a characterization.

(18) procedure based on preparative GPC fractionation to isolate the bio-crude from the liquefaction solvent. Furthermore, the heavy and light fractions of the bio-crude could be separated and analysed independently. Two liquefaction bio-crudes were studied and compared to fast pyrolysis oil. In chapter 3 we observed that formation of heavy species in the bio-crude is a major drawback of the liquefaction process. Furthermore, char formation should be minimized to increase the efficiency of the process. Chapter 5 focuses on the liquefaction of wood and its main components (namely cellulose, hemicellulose and lignin). The aim of this chapter is to reveal the reaction mechanisms occurring during. understood. Chapter 6 studies the effect that the liquefaction medium has on the. Chapter 1: Introduction. product distribution. Based on the obtained results, we were able to define how the. |. optimum liquefaction medium that would maximize oil yield and prevent char. 9. lignocellulose liquefaction and to determine the origin of the undesired products (heavy species in the bio-crude, char and gas). In chapter 3 we observed that different liquefaction media lead to different product distribution. However, the role of the medium during liquefaction is not yet fully. formation would be. Chapter 7 summarizes all the work presented in this thesis and draws overall conclusions linking all the results presented in the various chapters..

(19) 4. References 1.. Groeneveld, M.J., The change from fossil to solar and biofuels needs our energy. Inaugural lecture., in TCCB. 2008, university of Twente: Enschede.. 2.. Steffen, W., Crutzen, P.J., and McNeill, J.R., The Anthropocene: Are Humans Now Overwhelming the Great Forces of Nature. AMBIO: A Journal of the Human Environment, 2007. 36(8): p. 614-621.. 3.. Steffen, W., Richardson, K., Rockström, J., Cornell, S.E., Fetzer, I., Bennett, E.M., Biggs, R., Carpenter, S.R., de Vries, W., de Wit, C.A., Folke, C., Gerten, D., Heinke, J., Mace, G.M., Persson, L.M., Ramanathan, V., Reyers, B., and Sörlin, S., Planetary boundaries: Guiding human development on a changing planet. Science, 2015. 347(6223).. 4.. Hofmann, D.J., Butler, J.H., and Tans, P.P., A new look at atmospheric carbon dioxide. Atmospheric Environment, 2009. 43(12): p. 2084-2086.. 5.. Shell International BV, Shell Energy Scenarios to 2050: Signals & Signposts. 2011.. 6.. Lange, J.P., Lignocellulose conversion: An introduction to chemistry, process and economics.. 10. Biofuels, Bioproducts and Biorefining, 2007. 1(1): p. 39-48.. |. 7.. Swaaij, W.v., Kersten, S., and Palz, W., Biomass power for the world. Pan Stanford Series. Chapter 1: Introduction. on Renewable Energy, ed. W. Palz. Vol. 6. 2015, Singapore: Pan Stanford Publishing. 8.. de Jong, W. and van Ommen, J.R., Introduction: socioeconomic aspects of biomass conversion, in Biomass as a Sustainable Energy Source for the Future. 2014, John Wiley & Sons, Inc. p. 135.. 9.. US. Energy. Information. Administration;. Total. energy;. 2016.. http://www.eia.gov/totalenergy/. 10.. International Energy Agency; Statistics; 2016. http://www.iea.org/statistics/.. 11.. International Energy Agency, Sustainable production of second-generation biofuels. 2010.. 12.. Anwar, Z., Gulfraz, M., and Irshad, M., Agro-industrial lignocellulosic biomass a key to unlock the future bio-energy: A brief review. Journal of Radiation Research and Applied Sciences, 2014. 7(2): p. 163-173.. 13.. Biomass as a Sustainable Energy Source for the Future. 2014, New Jersey: John Wiley & Sons, Inc..

(20) 14.. Lange, J.-P., Lewandowski, I., and Ayoub, P.M., Cellulosic Biofuels: A Sustainable Option for Transportation, in Sustainable Development in the Process Industries. 2010, John Wiley & Sons, Inc. p. 171-198.. 15.. Lange, J.-P., Lignocellulose Conversion: An Introduction to Chemistry, Process and Economics, in Catalysis for Renewables. 2007, Wiley-VCH Verlag GmbH & Co. KGaA. p. 21-51.. 16.. Rowell, R.M., Handbook of wood chemistry and wood composites. 2005, United States of America: CRC press.. 17.. Bouvier, J.M., Gelus, M., and Maugendre, S., Wood liquefaction—An overview. Applied Energy, 1988. 30(2): p. 85-98.. 19.. Huber, G.W., Iborra, S., and Corma, A., Synthesis of Transportation Fuels from Biomass: Chemistry, Catalysts, and Engineering. Chemical Reviews, 2006. 106(9): p. 4044-4098.. 20.. Demirbaş, A., Biomass resource facilities and biomass conversion processing for fuels and chemicals. Energy Conversion and Management, 2001. 42(11): p. 1357-1378.. 21.. Fatih Demirbas, M., Biorefineries for biofuel upgrading: A critical review. Applied Energy, 2009. 86, Supplement 1(0): p. S151-S161.. 22.. Akhtar, J. and Amin, N.A.S., A review on process conditions for optimum bio-oil yield in hydrothermal liquefaction of biomass. Renewable and Sustainable Energy Reviews, 2011. 15(3): p. 1615-1624.. 23.. van Rossum, G., Zhao, W., Castellvi Barnes, M., Lange, J.-P., and Kersten, S.R.A., Liquefaction of Lignocellulosic Biomass: Solvent, Process Parameter, and Recycle Oil Screening. ChemSusChem, 2013. 7(1): p. 253 – 259.. 24.. Kumar, S., Lange, J.-P., Van Rossum, G., and Kersten, S.R.A., Liquefaction of Lignocellulose: Process Parameter Study To Minimize Heavy Ends. Industrial & Engineering Chemistry Research, 2014. 53(29): p. 11668-11676.. 25.. Bridgwater, A.V., Review of fast pyrolysis of biomass and product upgrading. Biomass and Bioenergy, 2012. 38: p. 68-94.. 26.. Mohan, D., Pittman, C.U., and Steele, P.H., Pyrolysis of Wood/Biomass for Bio-oil: A Critical Review. Energy & Fuels, 2006. 20(3): p. 848-889.. |. and Chemical Reference Data, 2006. 35(1): p. 77-92.. Chapter 1: Introduction. Horvath, A.L., Solubility of Structurally Complicated Materials: I. Wood. Journal of Physical. 11. 18..

(21) 27.. Westerhof, R.J.M., Nygård, H.S., Van Swaaij, W.P.M., Kersten, S.R.A., and Brilman, D.W.F., Effect of particle geometry and microstructure on fast pyrolysis of beech wood. Energy and Fuels, 2012. 26(4): p. 2274-2280.. 28.. Piskorz, J., Radlein, D.S.A.G., Scott, D.S., and Czernik, S., Pretreatment of wood and cellulose for production of sugars by fast pyrolysis. Journal of Analytical and Applied Pyrolysis, 1989. 16(2): p. 127-142.. 29.. Kumar, S., Direct Liquefaction of Lignocellulose: Exploration, Design and Evaluation of Conceptual Processes, in Sustainable Process Technology. 2015, University of Twente: Netherlands. p. 166.. 30.. Moffatt, J.M. and Overend, R.P., Direct liquefaction of wood through solvolysis and catalytic hydrodeoxygenation: an engineering assessment. Biomass, 1985. 7(2): p. 99-123.. 31.. Toor, S.S., Rosendahl, L., and Rudolf, A., Hydrothermal liquefaction of biomass: A review of subcritical water technologies. Energy, 2011. 36(5): p. 2328-2342.. 32.. Huang, H.-j. and Yuan, X.-z., Recent progress in the direct liquefaction of typical biomass.. 12. Progress in Energy and Combustion Science, 2015. 49: p. 59-80.. |. 33.. Xiu, S. and Shahbazi, A., Bio-oil production and upgrading research: A review. Renewable. Chapter 1: Introduction. and Sustainable Energy Reviews, 2012. 16(7): p. 4406-4414. 34.. Elliott, D.C., Transportation fuels from biomass via fast pyrolysis and hydroprocessing. Wiley Interdisciplinary Reviews: Energy and Environment, 2013. 2(5): p. 525-533.. 35.. Bridgwater, A.V., Catalysis in thermal biomass conversion. Applied Catalysis A: General, 1994. 116(1–2): p. 5-47.. 36.. Staš, M., Kubička, D., Chudoba, J., and Pospíšil, M., Overview of analytical methods used for chemical characterization of pyrolysis bio-oil. Energy and Fuels, 2014. 28(1): p. 385-402.. 37.. Kanaujia, P.K., Sharma, Y.K., Garg, M.O., Tripathi, D., and Singh, R., Review of analytical strategies in the production and upgrading of bio-oils derived from lignocellulosic biomass. Journal of Analytical and Applied Pyrolysis, 2014. 105(0): p. 55-74.. 38.. Branca, C., Giudicianni, P., and Di Blasi, C., GC/MS Characterization of Liquids Generated from Low-Temperature Pyrolysis of Wood. Industrial & Engineering Chemistry Research, 2003. 42(14): p. 3190-3202.. 39.. Front Matter, in Catalysis for Renewables. 2007, Wiley-VCH Verlag GmbH & Co. KGaA. p. I-XXIII..



(24) Chapter 2 Reagents and experimental procedure.

(25) ABSTRACT This chapter contains all the information concerning the materials, experimental setups, procedures, and analytical equipment used to perform all the experiments and analyses presented in this thesis. Definitions and calculation methods are also introduced.. 16. | Chapter 2: Reagents and experimental procedure.

(26) 1. Materials and reagents Pine wood was purchased from Rettenmaier & Söhne GmbH (Germany), grinded. treated at 200°C during 60 minutes in 2.5 kg of an ethanol:water mixture (60:40 wt%) in a 5 L autoclave. The liquid product was slowly added onto cold water to precipitate the lignin, which was then filtered, washed and dried. Composition and characterization of the wood and the organosolv lignin are discussed in the following section (1.1). The chemicals and reagents used for the characterization and the experiments are shown in Table 1 and Table 2. Table 1. Chemicals used in the characterization. Chemical. Formula Distributor. Purity. Comments. Tetrahydrofuran (THF). C 4H 8O. Sigma Aldrich. 99.9 %. Used for GPC measurements Used for GPC fractionation. Deuterated methyl sulfoxide (DMSO). C 2 D 6 OS. Acros Organics. 99.8 %. Used for 13C-NMR measurements Contained 0.03% of trimethyl silane. Sigma Aldrich. 99.99 % Used for 13C-NMR measurements. Chromium (III) acetylacetonate. Cr(AcAc). Deuterated acetone. C 3D6O. VWR. 99.8 %. Acetone. C 3H 6O. Sigma Aldrich. >99.5 % Used for GC-MS measurements. Acetone. C 3H 6O. Atlas Assink Chemie. >99.5 %. Used for product recovery and washing of solid residue. Hydranal Composite 5. -. Sigma Aldrich. -. Used for KFT measurements. Sigma Aldrich Sigma Aldrich. ≥99.9 % Used for KFT measurements ≥99.8 %. 3. Methanol:dichloromethane CH 4 O CH 2 Cl 2 (volume ratio of 3:1). Used for 1H-NMR measurements. |. method described by Huijgen et al [1]. Approximately 300 grams of wood were. 17. Organosolv lignin was prepared from the pine wood described above following the. Chapter 2: Reagents and experimental procedure. and sieved to a particle size below 0.5 mm and, finally, dried at 105°C for 24 hours..

(27) Table 2. Chemicals used in the experiments. Chemical. Formula. Distributor. Purity. C 7H 8O2 C 6 H 12 O 2 C 11 H 24. Sigma Aldrich Sigma Aldrich Sigma Aldrich. > 98 % 99 % > 99%. C 7H 8O2. Sigma Aldrich. > 98 %. C 11 H 10 C 6 H 10 O 5 C 6 H 10 O 5 C 6 H 12 O 6. Acros Organics® Sigma Aldrich Sigma Aldrich Sigma Aldrich. > 97 % > 99.5%. 1-Methylnaphthalene Tetralin (1,2,3,4-Tetrahydronaphthalene) Phenanthrene Naphthalene Toluene 2,6-Diethylnaphthalene Decalin (cis + trans-Decahydronaphthalene) n-Undecane 1-Methoxynaphthalene 1,2-Dimethoxybenzene Anisole (Methoxybenzene) Guaiacol (2-Methoxyphenol) Catechol (1,2-Dihydroxybenzene) Phenol 1-Naphthol (1-Hydroxynaphthalene) Pyrogallol (1,2,3-Trihydroxybenzene) Hexanoic acid Hexanol. C 11 H 10 C 10 H 12 C 14 H 10 C 10 H 8 C 7H 8 C 14 H 16 C 10 H 18 C 11 H 24 C 11 H 10 O C 8 H 10 O 2 C 7H 8O C 7H 8O2 C 6H 6O2 C 6H 6O C 10 H 8 O C 6H 6O3 C 6 H 12 O 2 C 6 H 14 O. Acros Organics® Sigma Aldrich Sigma Aldrich Sigma Aldrich Sigma Aldrich Sigma Aldrich Sigma Aldrich Sigma Aldrich Sigma Aldrich Sigma Aldrich Sigma Aldrich Sigma Aldrich Sigma Aldrich Sigma Aldrich Sigma Aldrich Sigma Aldrich Sigma Aldrich Sigma Aldrich. > 97 % 99 % 98 % > 99 % > 99,9 % > 97 % 98 % > 99 % > 98 % 99 % > 99 % > 98 % > 99 % > 99 % > 99 % > 99 % 99 % 98 %. CGO (Cracked Gas Oil)a. C 1.0 H 1.2 N 0,005 S 0,005. Shell Global Solutions International B.V.. -. LCO (Light Cycle Oil) a. C 1.0 H 1.4 N 0,01 S 0,01. Shell Global Solutions International B.V.. -. VGO (Vacuum Gas Oil) a. C 1.0 H 1.7 N 0,01 S 0,01. Shell Global Solutions International B.V.. -. Hydrowax a. C 1.0 H 1.7 N 0,02 S 0,01. Shell Global Solutions International B.V.. -. Chapter 3 Guaiacol (2-Methoxyphenol) Hexanoic acid n-Undecane. Chapter 4 Guaiacol (2-Methoxyphenol). Chapter 5 1-Methylnaphthalene Cellulose (Avicel PH-101) Amylopectin from maize D-(+)-Glucose. Chapter 6. 18. | Chapter 2: Reagents and experimental procedure a. More details in the characterization of the refinery streams can be found in the following. section (1.1).

(28) 1.1. Characterization of materials and reagents Wood composition is shown in Table 3. The Organosolv lignin was characterized. Table 3. Pine wood composition. Chemical analysis. wt%, dry. Cellulose Hemicellulose Lignin Total ash. 35 29 28 1. Elemental analysis. wt%, dry. C H O (by difference) N S. 46.6 6.3 47.0 0.04 0.06. Table 4. Characterization results of Organosolv lignin (the range of NMR chemical shifts are defined in sections 7.3 and 7.4). Elemental analysis. wt%, dry. C H O (by difference) N. 65.8 6.3 27.8 0.1. 13. C-NMR. C%. Paraffin Ethers / alcohols / Acetals Aromatics Carboxyls / carbonyls. 14.1 21.7 59.0 5.2. 1. H-NMR. H%. Paraffin Ethers / alcohols Aromatics Carboxyls / carbonyls. 28.5 44.5 26.0 1.0. |. 5), EA, 1H- and 13C-NMR (Table 5).. 19. (Table 4). The refinery streams were also analysed with GPC (Figure 1b and Table. Chapter 2: Reagents and experimental procedure. with GPC (Figure 1a), Elemental analysis (EA, CHNO analysis), 1H- and 13C-NMR.

(29) Table 5. Characterization results of the refinery streams (the range of NMR chemical shifts for refinery streams are defined in sections 7.3 and 7.4). CGO. LCO. VGO. Hydrowax. 89.3 9.0 1.1 0.5. 86.3 10.3 2.9 0.6. 85.5 11.9 2.0 0.7. 83.6 11.5 4.1 0.5. 35.4 64.6. 39.0 61.0. 77.0 23.0. 89.4 10.6. 68.8 7.2 24.0. 81.6 0.5 17.9. 95.1 0.0 4.9. 97.2 0.0 2.8. 66 117 1.8. 73 118 1.6. 228 369 1.6. 334 562 1.7. 160-370. 150-400. 200-540. > 280. Elemental analysis (wt%, dry) C H S (by difference) N C-NMR (C%). 13. Paraffins Olefins / Aromatics H-NMR (H%). 1. Paraffins Olefins Aromatics GPC. 20. Mn (Da) a Mw (Da) a ĐM b. |. Other. a. Number weighted molecular weight (Mn), Mass weighted molecular weight (Mw).. b. Dispersity (Đ M ) was calculated as Mw/Mn. It gives an indication of the distribution or the. heterogeneity of the Mw in the refinery stream.. a. b. CGO VGO. LCO Hydrowax. Normalised RID signal (a.u.). Normalised RID signal (a.u.). Chapter 2: Reagents and experimental procedure. Boiling range (°C). 10. 100. 1000. 10000. Molecular weightGPC (Da). 100000. 10. 100. 1000. Molecular weight. GPC. 10000 (Da). Figure 1. Molecular weight distribution of Organosolv lignin and refinery streams..

(30) 2. Liquefaction and product recovery Pine wood and the liquefaction medium were introduced in a 45 ml autoclave made. into a fluidised sand bed at the reaction temperature and, after liquefaction, moved to a cold water bath to stop the reactions. An initial heating rate of approximately 60°C/min allowed to reach 90% of the reaction temperature within the first 4 minutes and the targeted temperature some 5 min later. The heating time was included in the reaction time. Pressures and temperatures during the experiments were recorded using the Pico Log program. Three products were obtained after liquefaction, namely gas, bio-crude and solid. After cooling down of the reactor, gas was released, and the free gas volume at atmospheric pressure was measured. A sample was taken for GC analysis. Afterwards, the autoclave was opened and the slurry was filtered to provide a liquid product and a solid filter cake. The reactor was then rinsed with acetone and the wash liquor was filtered over the filter cake. The filter cake was dried at 105°C before quantification and analysis. The liquefaction liquid (bio-crude) was composed of two phases after acetone removal: a paste-like product named tar and a lighter product named oil. The total amount of product (solid, bio-crude and gas) typically amounted to more than 90w% of the total intake (biomass and solvent). Figure 3 shows a scheme of the procedure followed for the recovery of the liquefaction products.. 3. Recycling experiments For the recycling experiments, guaiacol was used as start-up solvent. For the first run, the autoclave (Figure 2) was loaded with pine wood (10 wt%), water (10 wt%) and guaiacol (80 wt%), and heated. After reaction, instead of cooling down to room. |. removal and a leak test. Afterwards, the autoclave was automatically submerged. 21. Figure 2). The autoclave was then closed tightly and flushed with N 2 for oxygen. Chapter 2: Reagents and experimental procedure. of Inconel 825 and equipped with a mechanical stirrer (autoclave set-up depicted in.

(31) temperature, the autoclave was now cooled to 200°C and opened to vent off the gas and remove compounds with a low boiling point (referred to as lights in chapter 3), which were condensed and quantified. The autoclave was then cooled down to room temperature and the product bio-crude in solution was obtained via filtration. This bio-crude was then used as solvent medium for the subsequent experiment. A total of 5 experiments (4 refills) were done. In the fifth run, 20wt% of wood and 10 wt% of water were loaded.. 22. | Chapter 2: Reagents and experimental procedure Figure 2. Scheme of the liquefaction set-up..

(32) Liquefaction medium. Liquefaction Slurry. Bio-crude Filtration. Oil. Filter cake. Filtration. Acetone removal. Tar. Filter cake. Solid. 23. Drying. Chapter 2: Reagents and experimental procedure. Gas. |. Reactor wall rinsed with acetone. Biomass. Figure 3. Procedure followed for the recovery of the liquefaction products.. 4. Fast pyrolysis Pyrolysis oil was produced in a continuous fluidized bed reactor that used sand as fluidized bed particles. The vapours formed were directed to a condenser system composed by two counter-current spray condensers and an intensive cooler placed in series. The non-condensable gases were collected and analysed for mass balance closure. The char produced was calculated by subtracting the initial amount of sand to the total solid residue. The condensates were mixed to obtain the fast pyrolysis oil. A detailed description of the fast pyrolysis procedure and setup can be found in [2]. Characterization results of the pyrolysis oil can be found in chapter 4..

(33) 5. Fractionation To do the GPC preparative fractionation, the sample was dissolved in THF and filtered through a 0.45 μm syringe filter. A multidraw kit allowed the injection of 1.5 ml of sample into an Agilent Technologies 1200 system composed of a pre-column (PLgel 25x25mm), a column (PLgel 300x25mm with 5μm, 500A) and a fraction collector. The fractionation was performed at room temperature for 50 minutes, and various bio-crude fractions were collected in intervals of one minute. The THF of the obtained fractions was evaporated under vacuum (10-20 mbar) and at 35°C to obtain the isolated bio-crude fractions. Figure 4 shows the fractions obtained after GPC preparative fractionation of biocrude. More details about GPC preparative fractionation can be found in chapter 4 and in the supporting information (section B).. 24. Guaiacol peak. Chapter 2: Reagents and experimental procedure. Normalised RID signal (a.u.). |. Initial oil Sum of oil fractions. 40. 400. 4000. 40000. Molecular weightGPC (Da). Figure 4. GPC chromatograms for a bio-crude fractionation. Mw GPC distribution of a liquefaction liquid product (bio-crude with the solvent), some of its fractions obtained by GPC fractionation and the sum of all these obtained fractions. The fractionated liquid product was obtained after liquefaction of wood (10 wt%) in guaiacol (90 wt%) at 300°C during 30 minutes..

(34) 6. Product definition and calculation. residue includes all the acetone insoluble compounds. All the yields presented in this paper (with the exception of the recycling experiments) are expressed in carbon percentage (C%) and are calculated using the following equations:. Gas yield (C%) =. mole of carbon in gas ∗ 12 ∗ 100 gram of wood input ∗ carbon content of wood. Solid yield (C%) =. Equation 1. gram of solid ∗ carbon content of solid ∗ 100 gram of wood input ∗ carbon content of wood. Biocrude yield (C%) = 100 – Gas yield – Solid yield Biocrude yield (C%) =. gram of biocrude ∗ carbon content of biocrude ∗ 100 gram of wood input ∗ carbon content of wood. Equation 2. (liquefaction). Equation 3. (pyrolysis). Equation 4. To calculate the gas yield, the volume percentages measured with a Micro-GC (section 7.7) were converted into mole percentages using the ideal gas law. Once the number of moles of each gas component was known, the total grams of carbon in the gas could be easily calculated. Carbon percentage of the liquefaction solids and the pyrolysis oils was directly analysed with the EA. Unfortunately, no EA could be performed for the solid residue of the pyrolysis experiment since it was mixed with the sand used in the fluidized bed. Therefore, the carbon content of the pyrolysis solid was obtained from literature [3], and corresponded to the char produced during pyrolysis of pine shave at 500°C.. |. condensable gases, bio-crude refers to the acetone soluble compounds and solid. 25. For both liquefaction and pyrolysis experiments, gas refers to all the non-. Chapter 2: Reagents and experimental procedure. 6.1. Product yields.

(35) Due to the nature of the recycling experiments, product yields had to be reported in weight percentage. The solid and gas yields were calculated dividing the grams of solid and gas produced by the initial grams of wood. Bio-crude yield was calculated by difference (biocrude yield = 100 – solid yield – gas yield).. 6.2. Heavy and light bio-crude In the following chapters, we use the terms ‘Vacuum Residue’ (VR) and ‘Distillate’ to refer, respectively, to the heavy and light species present in the bio-crude or liquid product. VR is defined as all the components in the liquid with an Mw GPC higher than 1000 Da, and Distillate comprises the liquid fraction with Mw GPC lower than 1000 Da (excluding the liquefaction solvent, Figure 5). The percentages of VR and Distillate are calculated using the GPC chromatogram of the studied liquid. The RID signal is plotted versus the elution time, and the area corresponding to the VR. 26. (Mw GPC > 1000 Da) or to the Distillate (Mw GPC < 1000; excluding the liquefaction. |. solvent peak) is divided by the total area (see Equation 5 and Equation 6). The cut. Chapter 2: Reagents and experimental procedure. point between the solvent and the Distillate is defined as the minimum seen in GPC trace just after the solvent peak. It varies from 72 to 250 Da depending on the solvent used as liquefaction media. A visual inspection of the various GPC traces shown in this thesis reveals that the variation in cut point is bringing only a modest uncertainty to the overall integral of the bio-crude part of the GPC trace.. VR fraction (%) =. RID area corresponding to MwGPC > 1000 Da Total RID area (excluding solvent peak). Distillate fraction (%) =. RID area corresponding to MwGPC < 1000 Da (excl. solvent peak) Total RID area (excluding solvent peak). Equation 5. Equation 6. The yields of VR and Distillate are calculated using the following equations:.

(36) Distillate Yield (C%) = Biocrude yield ∗ Distillate fraction. Equation 8. Solvent. VR. Distillate 10. 100. 1000. 10000. Figure 5. Scheme of the procedure followed for the quantification of heavies in the bio-crude.. 6.3. Bio-crude composition and quality Various parameters have been used to report the composition and the quality of the bio-crude. In chapters 4 and 5, quantitative 13C-NMR and 1H-NMR are used to determine the yield or content of aromatic, paraffinic or oxygenated species in the liquid products or organosolv lignin. Equation 9 and Equation 10 are used to calculate the yield of liquid aromatic species, and the aromatics with lignin origin respectively.. 27. |. Molecular weightGPC (Da). Chapter 2: Reagents and experimental procedure. Equation 7. Intensity (a.u.). 𝑉𝑉𝑉𝑉 𝑌𝑌𝑌𝑌𝑌𝑌𝑌𝑌𝑌𝑌 (𝐶𝐶%) = 𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵 𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦 ∗ 𝑉𝑉𝑉𝑉 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓.

(37) Yield of liquid aromatics (C%) = Liquid yield ∗ Aromatic content in the liquid. Equation 9 Equation 10. Aromaticslignin (C%) =. Lignin content of wood ∗ Carbon content of lignin ∗ Aromatic content of lignin ∗ 100 Carbon content of wood. These equations are expressed in C% and, therefore, the aromatic content is determined by. C-NMR. Equivalent equations could be used to make the. 13. calculations in H% (using 1H-NMR results) or to calculate the yields of paraffinic or oxygenated species. Effective H/C ratio (H/C eff ) and Higher heating value (HHV) were used as indicators of bio-crude quality in chapters 4 and 5. The H/C eff gives an estimation of the hydrogen left in the product once all the oxygen is removed as water (Equation 11).. |. all the combustion products are cooled down to the initial temperature of the fuel.. Chapter 2: Reagents and experimental procedure. 28. The HHV is the amount of heat produced when a fuel is completely combusted and By returning the final products to the pre-combustion temperature, the latent heat of vaporization of the water steam is included in the HHV. The HHV is calculated with the Reed’s formula [4] (Equation 12).. H⁄Ceff =. mole hydrogen − 2 ∗ mole oxygen mole carbon. HHV (MJ⁄kg) = 0.341 ∗ carbon wt% + 1.322 ∗ hydrogen wt% − 0.12 ∗ oxygen wt%. Equation 11. Equation 12. 6.4. Calculation of solubility parameters The Hildebrand solubility parameter (δ) of a component is defined as the square root of the cohesive energy density. It represents the energy needed to evaporate an elementary volume of this solvent, and it is generally used to study the interaction.

(38) between materials. The Hildebrand value can be calculated with the following. ΔH𝑣𝑣 – RT δ= � Vm. Equation 13. where ΔH v is the enthalpy of vaporization, R the ideal gas constant, T the temperature and V m the molar volume of the pure solvent. Materials with similar Hildebrand values are likely to be miscible. However, this parameter does not consider certain type of associations such as polar interaction or hydrogen-bonding. As a consequence, occasionally, two materials might have similar Hildebrand values but be immiscible. One solution to this problem was formulated by Hansen et al. [6]. They proposed that the total energy of vaporization parameter into three partial solubility parameters, namely dispersion (δ D ), polarity. |. (δ P ) and H-bonding (δ H ). The relation between the Hildebrand and the partial. 29. consists of several individual parts, and divided the Hildebrand solubility. Chapter 2: Reagents and experimental procedure. equation [5]:. Hansen solubility parameters is described by equation [6]:. δ = �δ𝐷𝐷 2 + δ𝑃𝑃 2 + δ𝐻𝐻 2. Equation 14. The solubility parameters of solvent mixtures can be calculated with the following equation [6]:. δ(D,P,H) = ɸ1 ∗ δ(D,P,H)1 + ɸ2 ∗ δ(D,P,H)2 + ɸ3 ∗ δ(D,P,H)3. being φ 1,2,3 the volume fractions of each solvent.. Equation 15.

(39) The solubility radius (Ra) around a solute defines the combination of δ D , δ P and δ H of solvent that offer similar interaction with the solute. The lower the Ra, the higher the interaction. Ra can be calculated with the equation [6]: 𝑅𝑅𝑅𝑅 = �4 ∗ (δD2 − δD1 )2 + (δP2 − δP1 )2 + (δH2 − δH1 )2. Equation 16. The Hildebrand and Hansen partial solubility parameters used in this work were obtained from [6]. According to [6], Hansen solubility parameters of complex components such as cellulose and lignin were calculated by studying their solubility or degree of swelling in a series of well-defined solvents. The Hansen parameters of the refinery streams were estimated by comparing each refinery stream average structure with known molecules (see section 1.1).. 7. Characterization techniques 30. | Chapter 2: Reagents and experimental procedure. 7.1. Gel Permeation Chromatography (GPC) The Mw distribution of liquids and organosolv lignin was determined with GPC. The analyses were performed with a system from Agilent Technologies 1200 composed by three columns placed in series (7.5 × 300 mm, particle size 3 μm) packed with a highly crosslinked polystyrene–divinylbenzene copolymer gel (Varian, PLgelMIXED-bed E), a refractive index-detector (RID) and an Variable wavelength detector (VWD) operated at 254 nm. Bio-crudes were dissolved in THF and filtered through a 0.45 μm syringe filter. Then, 20 μl of sample were injected into the system operated at 40°C and with a flow of 1 ml/min of THF. Measurements lasted 40 minutes. The calibration line made with polystyrene standards of several molecular weights (162-29510 g/mole) was used for the conversion of elution volume to molecular weight (Mw GPC )..

(40) 7.2. Fourier Transform Infrared Spectroscopy (FTIR) Qualitative FTIR analyses were performed with a Fourier Transform Infrared. 16 scans were performed. Afterwards, the spectra were baseline corrected and normalized.. 7.3. 13C Nuclear Magnetic Resonance (13C-NMR) Quantitative. C-NMR measurements were performed with a Bruker 600 MHz-. 13. Avance II NMR spectrometer. Samples were prepared by dissolving approximately 0.25 g of (solvent-free) sample and 0.024 g of Cr(AcAc) 3 (relaxation agent) in 0.7 ml of deuterated DMSO. Measurements were performed at 40°C using the ‘inverse gate decoupling’ method with 5 seconds of relaxation time and 5000 scans. The DMSO signal was used as internal reference. Manual integration of the spectra was performed with MestReNova LITE software (version 5.2.5-5780). When present, solvent peaks (DMSO, acetone or THF) were manually integrated and subtracted from the corresponding region. The integration regions were defined according to Ben et.al and Ingram et.al [7, 8] and are shown in Table 6. C-NMR analyses of refinery streams were performed with a Bruker 400 MHz-. 13. Ascend NMR spectrometer using ‘inverse gate decoupling’ with 5 seconds of relaxation time and 1024 scans. Samples were prepared as described previously. However, Hydrowax was not soluble in pure DMSO and, therefore, it was dissolved a mixture of cyclohexane and deuterated DMSO.. |. was measured in the range 650 to 4000 cm-1 with an spectral resolution of 4 cm-1, and. 31. system (ATR) and a deuterated triglycine sulphate detector (DTGS). Absorbance. Chapter 2: Reagents and experimental procedure. Spectrophotometer from Bruker equipped with an Attenuated total reflection.

(41) Table 6. Integration regions for 13C-NMR. Functional group Alkanes (aliphatic C-C bond). Integration region. Examples H3C. R H2. C. (methoxy groups). 55.2-60.8 ppm. R'. R'. R. 54-105 ppm. H2. 84-105 ppm. C. C. H. R'. R''. R''. R'. C R. O. H 3C. R O. R''. O. (acetals). R. R'''. 1-54 ppm. Aliphatic alcohol/ ethers/acetals. R. R. CH R'. O. O R. HO. Aromatics. C. 105-166 ppm. R. C. C. C. 32. R. O. | Chapter 2: Reagents and experimental procedure. Carbonyls/carboxyls. 166-210 ppm. O. C R. C. R' O. R. R'. 7.4. 1H Nuclear Magnetic Resonance (1H-NMR) For 1H-NMR quantitative analyses, approximately 0.1 g of sample was dissolved in 0.7 ml of deuterated acetone. Hydrowax was dissolved a mixture of cyclohexane and deuterated acetone. The analyses were performed with a Bruker 400 MHz-Ascend NMR spectrometer. A relaxation time of 2 seconds and 128 scans were used. Integration of the spectra was performed following the same procedure described for 13C-NMR. The assignation of the peaks for 1H-NMR was based on the papers from Ingram et.al and Mullen et.al [8, 9]. Integration regions are shown in Table 7. When visible, the broad band corresponding to the hydrogen in alcohol groups appeared under 3 ppm (region of the Aliphatic α to an unsaturation or an heteroatom). Only three.

(42) integration regions were defined for the refinery streams, namely alkanes (0-4.5 ppm), olefins (4.5-6.5 ppm) and aromatics (6.5-9.0 ppm) [10, 11].. Functional group. Integration region. Alkanes. 0.5 – 3.0 ppm. Aliphatic β or further to an unsaturation or an heteroatom. 0.5 - 1.5 ppm. Examples. H2 C. R. CH3 R. CH3. Aliphatic α to an unsaturation or an heteroatom. 1.5 - 3.0 ppm. Aliphatics in a C bonded to an alcohols, ether or two aromatics. 3.0 - 5.6 ppm. Alcohols, ethers and methylenedibenzene. 3.0 - 5.0 ppm. CH3. R CH3. R'. O. 5.0 - 5.6 ppm. R. H2. R''. CH O. Aromatics or heteroaromatics. C. O. 33. C. |. H2 R. Acetals. O. R'. O. 5.6 - 9.0 ppm. H. H. O. Aldehydes. 9.0 - 12.0ppm R'. Chapter 2: Reagents and experimental procedure. Table 7. Integration regions for 1H-NMR.. H. 7.5. Elemental Analysis (EA) The carbon, hydrogen and nitrogen content of solid and liquid products was determined with an Elemental Analyser Inter Science Flash 2000. The oxygen (sulphur in refinery streams) content of the samples was calculated by difference..

(43) 7.6. Micro Carbon Residue Test (MCRT) The carbon residue was measured with a Micro Carbon Residue tester ACR-M3 Zematra.. 7.7. Gas analysis Gas analyses were performed with a Micro-Gas Chromatograph (Variant CP-4900) equipped with two columns. The first column (Molsieve 5A (10 m)) detected H 2 , O 2 , N 2 , CH 4 and CO, while the second column (PPQ (10 m)) detected CO 2 , C 2 H 4 , C 2 H 6 , C 3 H 6 and C 3 H 8 . Helium was used as a carrier gas.. 7.8. Gas Chromatography-Mass Spectrometry (GC-MS) GC-MS analyses were performed with a gas chromatograph equipped with a mass. 34. |. spectrometer (GC 7890A MS 5975C, Agilent Technologies). Samples were first. Chapter 2: Reagents and experimental procedure. dissolved in acetone (5 wt%) and filtered through a 0.2 μm Whatman filter. Then, 1 µL of sample was injected into the injector port set at 250°C and with a split ratio of 20:1. The capillary column (Varian CP9154, 60 m, 0.25 mm) was packed with 0.25 µm of 14% cyanopropyl-phenyl and 86% PDMS, and operated at a constant Helium flow of 2 ml/min for 106 min. Oven temperature was set at 45°C for 4 min, then increased at a rate of 3°C/min and finally maintained at 280°C for 20 min. The mass spectrometer was operated under electron ionization mode (70 eV), with a frequency of 1 scan/s, and detected a m/z range between 15 and 500. A spectral library (NIST Mass Spectral Library Version 08) was used to identify the detected compounds.. 7.9. Scanning Electron Microscopy (HR-SEM) The morphology of chars was studied with Scanning Electron Microscopy (Analysis Zeiss MERLIN HR-SEM). The system was equipped with a Hot Field Emission Gun.

(44) and a detector HE-SE2. Measurements were done using a voltage of 0.85 kV and a prove current of 15-60 pA.. of ethanol:dichloromethane (3:1 in volume) was used as solvent.. 7.11. Viscosity measurements Viscosity of the oils was measured with a rotary viscometer Brookfield DV-E at 30°C.. |. a Metrohm 787 KF Titrino. Hydranal Composite 5 was used as titrant and a solution. 35. The water concentration in the liquid was determined by Karl-Fischer titration using. Chapter 2: Reagents and experimental procedure. 7.10. Karl-Fischer titration (KFT).

(45) 8. References 1.. Huijgen, W.J.J., A.T. Smit, P.J. de Wild, and H. den Uil, Fractionation of wheat straw by prehydrolysis, organosolv delignification and enzymatic hydrolysis for production of sugars and lignin. Bioresource Technology, 2012. 114(0): p. 389-398.. 2.. Westerhof, R.J.M., D.W.F. Brilman, M. Garcia-Perez, Z. Wang, S.R.G. Oudenhoven, W.P.M. van Swaaij, and S.R.A. Kersten, Fractional Condensation of Biomass Pyrolysis Vapors. Energy & Fuels, 2011. 25(4): p. 1817-1829.. 3.. Ahmad, M., A.U. Rajapaksha, J.E. Lim, M. Zhang, N. Bolan, D. Mohan, M. Vithanage, S.S. Lee, and Y.S. Ok, Biochar as a sorbent for contaminant management in soil and water: A review. Chemosphere, 2014. 99(0): p. 19-33.. 4.. Domalski, E.S., T.L.J. Jobe, and T.A. Milne, Thermodynamic data for biomass conversion and waste incineration. 1987, American Society of Mechanical Engineers, New York.. 5.. Hildebrand, J. and R.L. Scott, The Solubility of Nonelectrolytes. 3rd ed, ed. A.C. Society. 1950, New York: Reinhold.. 36. 6.. Hansen, C.M., Hansen solubility parameters: A user's handbook. 2000, United States of. |. America: CRC Press LLC.. Chapter 2: Reagents and experimental procedure. 7.. Ben, H. and A.J. Ragauskas, NMR Characterization of Pyrolysis Oils from Kraft Lignin. Energy & Fuels, 2011. 25(5): p. 2322-2332.. 8.. Ingram, L., D. Mohan, M. Bricka, P. Steele, D. Strobel, D. Crocker, B. Mitchell, J. Mohammad, K. Cantrell, and C.U. Pittman, Pyrolysis of Wood and Bark in an Auger Reactor: Physical Properties and Chemical Analysis of the Produced Bio-oils. Energy & Fuels, 2007. 22(1): p. 614-625.. 9.. Mullen, C.A., G.D. Strahan, and A.A. Boateng, Characterization of Various Fast-Pyrolysis Bio-Oils by NMR Spectroscopy†. Energy & Fuels, 2009. 23(5): p. 2707-2718.. 10.. Sarpal, A.S., G.S. Kapur, S. Mukherjee, and A.K. Tiwari, PONA analyses of cracked gasoline by 1H NMR spectroscopy. Part II. Fuel, 2001. 80(4): p. 521-528.. 11.. Burri, J., R. Crockett, R. Hany, and D. Rentsch, Gasoline composition determined by 1H NMR spectroscopy. Fuel, 2004. 83(2): p. 187-193..

(46) 37. |. Chapter 2: Reagents and experimental procedure.

(47) 38. |. Chapter 2: Reagents and experimental procedure.

(48) Chapter 3 Solvent, process parameter and recycle bio-crude screening.

(49) ABSTRACT Liquefaction of lignocellulosic biomass was studied for the production of liquid (transportation) fuels. The process concept used a product recycle as liquefaction medium and produced a bio-crude that can be co-processed in a conventional oil refinery. This all was done at medium temperature (~ 300 °C) and pressure (~ 60 bar). Solvent screening experiments showed that oxygenated solvents are preferred as they allow high bio-crude (up to 93 % on carbon basis) and low solid yields (~1-2 % on carbon basis) and, thereby outperform liquefaction of biomass in compressed water and biomass pyrolysis. The following solvent ranking was obtained: guaiacol > hexanoic acid >> n-undecane. The usage of wet biomass resulted in higher biocrude yields than dry biomass. However, it also resulted in higher operating. 40. pressure, which would make the process more expensive. Refill experiments were. |. also performed to evaluate the possibility to recycle the bio-crude as liquefaction. Chapter 3: Solvent, process parameter and recycle bio-crude screening. medium. The recycle bio-crude appeared to be very effective in liquefying the biomass, even surpassing the start-up solvent guaiacol, but became increasingly heavy and more viscous after each refill and eventually showed a molecular weight distribution which resembled that of refinery vacuum residue.. This chapter has been published as: van Rossum, G.; Zhao, W.; Castellvi Barnes, M.; Lange, J.-P. and Kersten, S. R. A.; Liquefaction of Lignocellulosic Biomass: Solvent, Process Parameter, and Recycle Oil Screening. ChemSusChem, 2013, 7(1): p. 253-259..

(50) example, 6 – 30 wt% [1, 2] versus 35-40 wt% for pyrolysis bio-crude [3] and 40-50 wt% for the initial lignocellulose. The process temperature is milder than in pyrolysis (up to ~ 400 °C) but the use of solvent often results in higher pressures (up to ~ 250 bars if water is used as solvent). An overview of literature on biomass liquefaction is given in Table A1 (Supporting information). Solvent selection is very important to obtain high liquefaction bio-crude yields. Polar solvents usually perform better than apolar solvents. Combined bio-crude and gas yields up to 99 wt % have been reported for liquefaction with and without the use of a homogeneous and/or heterogeneous catalyst. From a commercial point of view, solvent cost should be minimized. Hence the solvent should either be cheap and easily recoverable, be produced within the process and/or be co-processed with the bio-crude to the end products. From as early as the 1970’s, processes have been developed to pilot scale based on two solvent types, namely water and wood liquefaction recycle bio-crude. Comprehensive overviews of direct liquefaction processes have been given by Behrendt et. al. [4] and Elliot et. al. [5]. These processes all had as main drawbacks that the product was not suitable for final upgrading to transportation fuels and/or that process conditions were too harsh to become economically viable. The processes with recycle bio-crude resulted mainly in a product bio-crude that was too viscous, and the use of water and/or reducing gas led to very high operating pressures (> 150 bar). Therefore processes have been developed up to pilot scale but have not reached commercialization. Hence, from a process and product quality point of view, further progress is still required. Recent efforts [6, 7] and this study have tried to gain more insight in the desired solvent properties and operating conditions for biomass liquefaction, in which high bio-crude yields are obtained with a moderate viscosity. In this chapter, we reported our initial efforts to improve the economics of biomass liquefaction [7]. Our approach was based on the idea that the process should:. Chapter 3: Solvent, process parameter and recycle bio-crude screening. is the liquefaction, which produces a bio-crude with moderate oxygen content, for. |. One of the various possible routes to convert (lignocellulosic) biomass into bio-crude. 41. 1. Introduction.

(51) •. operate without a catalyst to avoid contamination of the resulting bio-crude, which inevitably leads to elevated operating temperature,. •. operate at mild pressure by avoiding reactive gases such as CO or H 2 and by using a high-boiling solvent,. •. use an inexpensive solvent that does not require separation from the bio-crude, for example, by using a fraction of the bio-crude itself as solvent or by using a cheap refinery stream. Although inexpensive, water disqualified by its high vapour pressure at elevated temperature.. Hence, our research focused on a limited number of solvents that show fairly high boiling points (~200°C) and are model components for a bio-crude fraction or refinery streams, namely guaiacol, hexanoic acid and n-undecane. Guaiacol represents lignin degradation products, hexanoic acid represents carboxylic acids. 42. that are formed through cellulose and hemicellulose decomposition, and n-. |. undecane represents a refinery stream. As the liquefaction appeared to proceed best. Chapter 3: Solvent, process parameter and recycle bio-crude screening. with bio-crude model components, refill experiments were performed to simulate the recycle of bio-crude as the liquefaction medium. While the research was underway, another research group appeared to follow a similar approach to biomass liquefaction [6].. 2. Result and discussion 2.1. Solvent screening During liquefaction, biomass is depolymerized and broken down into smaller segments. The type of solvent used is of paramount importance for the obtainable yields of solid residue, bio-crude and gas. The solvent can (partly) dissolve original biomass polymers and its initial fragments, stabilize and dilute the products formed and also act as a reactant. The effect of solvent selection is clearly illustrated in Figure 1a, in which pine wood liquefaction results are shown as carbon distribution to solid,.

(52) and undecane. Both dry and wet (10 wt% on total feed basis) wood were used. In particular, wet biomass is of special interest as drying biomass is expensive and preferably minimized for each application. Additionally, a run in water and a run without any liquid (solvent-free/pyrolysis) were performed for comparison. The solid does not only have to be a product in the form of char/coke but can also be unconverted wood. The solvent type appeared to have a very big impact on the carbon distribution of the products. Aromatic and/or oxygenated solvents generally performed better than an aliphatic hydrocarbon. According to carbon converted to bio-crude, the solvent performance can be ranked as follows: guaiacol ≈ water > hexanoic acid >> undecane >> solvent-free/pyrolysis (Figure 1a)). A quick look at common solvent parameters (see table A4, Supporting information) did not reveal a clear correlation between the solvent and its effectiveness in liquefaction. Clearly, a more extensive set of solvents would be needed to unravel such correlation but this wt% wood, 10 w% water and 80 wt% of solvent) led to a higher bio-crude yield for. |. every solvent used (Figures 1a and 1b). As a downside, the operating pressures. 43. was not the purpose of the present study. Wet wood (50 % moisture, reported as 10. Chapter 3: Solvent, process parameter and recycle bio-crude screening. bio-crude and gas for the three different solvents, namely guaiacol, hexanoic acid,. where significantly increased (from 32 - 56 bar without water to 60 – 121 bar with water). The addition of water was further investigated with guaiacol and a minimum char yield was observed for intermediate water/guaiacol ratios between 1:4 and 4:1 (Figure 1b). This showed that a mixture of solvents can lead to an added beneficial effect. The conversions and effectiveness of solvents observed here were generally in agreement with data reported for similar solvents. Phenol, which is chemically similar to guaiacol, shows a very good performance for biomass liquefaction [8-11]. Hydrocarbon solvents like tetralin [12, 13], toluene [14] and “Shellsol” [15] give somewhat lower bio-crude yield. If water is used as a co-solvent, almost no solids and little gas are obtained for guaiacol (Figure 1) and phenol [9], which shows that the addition of water as a co-solvent is generally favourable. Water as a pure solvent.

(53) (e.g. hydrothermal liquefaction of wet biomass) generally results in lower bio-crude yields (up to 58 wt%) [2, 16]. Solid. Bio-crude. Gas. b. 60 Solid yield (C% based on dry wood intake). Pyrolysis HTL Guaiacol Guaiacol Hexanoic acid Hexanoic acid n-Undecane n-Undecane. n-Undecane. 50 40 30 Hexanoic acid. WOOD. a. 20 10 Guaiacol 0. 0 20 40 60 80 100 Yield (C% based on dry wood intake). 0. 20. 40 60 80 Water content (wt%). 100. Figure 1. (a) Products distribution obtained after liquefaction of wood (10 wt%) in guaiacol, hexanoic acid, and undecane with and without the addition of 10 wt% of water. The product distribution of wood pyrolysis (solvent-free) and wet wood liquefaction (HTL) is. 44. also shown. (b) Solid yields plotted versus water content using four different solvents. The. | Chapter 3: Solvent, process parameter and recycle bio-crude screening. temperature was ~ 300°C with a reaction time of 30 min. Details of the experiments can be found in Table A2 of the Supporting information.. 2.2. Product quality The bio-crude produced from the liquefaction of biomass still needs further processing if transportation fuels are desired. Co-processing with fossil crude oil (fractions) seems an attractive way for upgrading as use can be made of an already installed infrastructure and known technology. Promising results in this field have been obtained for a different route in which, on lab scale, biomass is added to a fluid catalytic cracking (FCC) unit by pyrolysis and hydrotreatment [17]. For this, however, there should be compatibility between the bio-crude and fossil stream. As an initial product quality evaluation, the molecular weight of bio-crudes produced in guaiacol, were compared with typical refinery streams (Figure 2). Wood liquefaction bio-crude showed a wide weight distribution, whereas the refinery.

(54) used, the molecular weight showed a heavy fraction (> 1 kDa) comparable with vacuum residue streams. If water was added, the heaviest components (>5 kDa) were typically consumed and/or not produced. However, the bio-crude was still significantly heavier than vacuum gas oil and would need a cracking/ depolymerisation (and likely hydrotreatment) step for high-end fuel production. The amount of bio-crude heavier than guaiacol (>150 Da) was determined by GPC and accounted for approximately 55 wt% of the wood intake, confirming that most of the wood is converted into relatively heavy bio-crude. Gas production was overall low. The major gaseous products were CO and CO 2 (~2 and 1 C% respectively, table A1 in Supporting information) with marginal amounts of CH 4 and higher hydrocarbons. The H 2 production was marginal compared to CO x (~ 2 mol% of the CO x ).. 45. Normalised RID signal (a.u.). |. Guaiacol (10 wt% water). Chapter 3: Solvent, process parameter and recycle bio-crude screening. streams are, as expected, cut off molecular weight distributions. If dry wood was. Vacuum residue. Guaiacol (0 wt% water) Vacuum gas oil 100. 1000. 10000. 100000. Molecular weightGPC (Da). Figure 2. GPC of wood liquefaction using guaiacol as a solvent with and without addition of water plotted together with data of typical refinery streams. Refractive index (arbitrary units) versus polystyrene calibrated molar mass..

(55) 2.3. Process parameters screening Process parameter screening was done for both guaiacol and hexanoic acid as wood liquefaction solvents. As both solvents gave similar trends, we will focus the discussion on the study of guaiacol, which was the most effective liquefaction solvent. The product carbon yield distribution for the process variables (a) wood loading, (b) temperature, (c) reaction time, and (d) water content are shown in Figure 3.. b. 80. Bio-crude. 60 40. 100. Yield (C% based on dry wood intake). 100. Yield (C% based on dry wood intake). a. Solid. 20 Gas. 46. 0. Bio-crude 80 60 Solid Ea = 101 kJ/mol k0 = 1.18*196 1/s. 40 20 Gas. 0 4. 6. 8. 10. 12. 14. 16. 260. 280. |. Wood loading (wt%). 300. 320. 340. Temperature (°C). d Bio-crude. 80 60 Solid Ea = 101 kJ/mol k0 = 1.18*196 1/s. 40 20. Gas. Yield (C% based on dry wood intake). 100. 100 Yield (C% based on dry wood intake). Chapter 3: Solvent, process parameter and recycle bio-crude screening. c. Bio-crude. 80 60 40 Solid. 20. Gas 0. 0 0. 20. 40. 60. 80. 100. Reaction time (min). 120. 0. 20. 40. 60. 80. Water content (wt%). Figure 3. Carbon product yield distribution versus (a) wood loading, (b) temperature (c) reaction time and (d) water content. Standard conditions for an experiment were: 10 wt% wood, ~30 min, ~300 °C and 0 wt% water, unless specified otherwise by the X-axis. The lines are illustrative except for solid yields versus temperature and reaction time, which are fitted to a first order reaction..

(56) yield. This suggested that a higher concentration of liquefaction intermediates/ products stimulated further liquefaction of biomass polymers. This effect was not observed with wood loading variation using hexanoic acid as a solvent. However, the mixture obtained at high wood loading was very viscous, and much higher loadings would only wet the wood instead of introducing free liquid. Temperature had the strongest effect on liquefaction; as the temperature increased, more solid was converted to bio-crude and permanent gas. The bio-crude yields showed a large increase, the gas yields increase linearly with temperature. The solid residue still had a fibrous appearance similar to the fed wood, which indicated that the solid seems to originate directly from the wood rather than from bio-crude degradation. Longer reaction times resulted in higher bio-crude yields and lower char yields. A small increase of gas yield was observed, which also resulted in a higher pressure (32 bar for 30 min compared to 45 bar for 120 min, see Table A1 in Supporting information). on the amount of bio-crude produced. Water is normally present in biomass and. |. expensive to remove by drying. Even very high amounts of water seemed to be. 47. As already seen with solvent screening, the addition of water had a beneficial effect. Chapter 3: Solvent, process parameter and recycle bio-crude screening. With increasing wood loading, the bio-crude yield increased as the expense of solid. beneficial at the cost of increasing operating pressure. Although limited, the data allowed a preliminary kinetic analysis of the liquefaction reaction. A first order reaction (Equation 1) was fitted to the temperature and time profiles reported in Figure 3 b-c:. X = 1 − e−kt. Equation 1. In which k = k 0 e−Ea /RT , X = (1-solid yield/100) is the conversion of the solid (the solid yield (in C%) is taken from Figure 3c and d), k [s-1] the first-order rate constant, t [s]. the reaction time, k 0 [s-1] a pre-exponential factor, E a [kJmol-1] the activation energy, R [kJmol-1K-1]=0.008314 the ideal gas constant, and T [K] the temperature. At the same time, the conversion (X) was defined as the decrease in solid residue, assuming that the solid mainly consisted of unconverted feed rather than of solid product.

(57) (char). For the temperature regime examined, this assumption held quite well; however, at higher temperatures a significant amount of char formation is expected. A very good fit was obtained for temperature and reaction time variation (Figure 3b and 3c) with an activation energy (E a ) of 101 kJ mol-1 with a pre-exponential factor (k 0 ) of 1.18*106 s-1.. 2.4. Process concept A possible conceptual process for biomass liquefaction is illustrated in Figure 4. Here biomass is converted in recycled bio-crude, after some tailoring. Light products (gas, water and light organic compounds) and heavy products (solid and very heavy biocrude) are removed, and the large amount of middle-range liquid is used as recycle and product bio-crude. This concept is interesting because it is very simple and could be used for primary conversion at the biomass product site. The product bio-. 48. crude could then be transported for the final upgrade, for example, by co-refining. |. with fossil streams. In this way, the volumetric energy density is increased. Chapter 3: Solvent, process parameter and recycle bio-crude screening. significantly and an initial purification step is applied. Lights. Biomass Liquefaction. Separation. Product bio-crude. Recycle Heavies. Figure 4. Conceptual process scheme for the liquefaction of biomass for the production of bio-crude.

(58) 4 3 2. 5 124 Guaiacol. 1. 100. 1000 10000 Molecular weightGPC (Da). 100000. Figure 5. Molecular weight distribution measured via GPC of 5 refill experiments. The insert shows the solvent guaiacol peak.. In an attempt to validate such a concept, a few refill experiments were performed heavy products were removed between every refill of wood. The light products were. |. removed by releasing the pressure at 200°C prior to the final cooling, and the heavy. 49. with guaiacol as the start-up solvent and wet wood. As proposed, the light and. Chapter 3: Solvent, process parameter and recycle bio-crude screening. RID signal (a.u.). 5. RID signal (a.u.). 1. products were removed by filtering the bio-crude through a 1 µm filter. With each refill experiment (see also Table A3 in Supporting information), the amount of original guaiacol was reduced to reach approximately 38 wt% (quantification made with GC-MS) of the initial intake in the last experiment (run 5). As shown in Figure 5 and Table A3 (Supporting information), the overall molecular weight and viscosity of the bio-crude increased with each refill. The overall molecular weight was, after the 5th run, in the same range (heavy end) as vacuum residue and would need significant upgrading for the production of transportation fuels. Interestingly, the effectiveness of the recycle bio-crude remained very high for only low amounts of solids remained after each experiment (< 1 wt% per refill, see Table A3, Supporting information). It even surpassed the performance of the start-up solvent guaiacol to reduce the amount of solid residue. A similar effect was observed in the process parameter study in which the bio-crude yield increased with increasing wood.

(59) loading (Figure 3a). Elemental analysis (Table A3, Supporting information) shows that significant deoxygenation took place after the fifth run as the oxygen content decreased from approximately 47 wt% in wood to approximately 32 wt% in the biocrude. Such an oxygen decrease is consistent with the liberation of water in the lights and CO and CO 2 found in the gas products. It should be specified that the elemental composition of the bio-crude was calculated from that of the liquid product after the contribution of water and guaiacol, which were present in the liquid product, were excluded.. 3. Conclusions This chapter reported our search for a cheap biomass liquefaction process that operates at mild pressure, mild temperature, without catalysts and without need for expensive solvent/bio-crude separation. The following could be concluded:. 50. •. |. Polar solvents are more effective than apolar ones as the solvent effectiveness. Chapter 3: Solvent, process parameter and recycle bio-crude screening. decreases in the order of guaiacol ≈ water > hexanoic acid >> n-undecane >> none. Polar solvents allowed deep liquefaction (>80%) at approximately 320°C without any catalyst. •. Wet wood led to a higher bio-crude yield and lighter bio-crude than dry wood for all solvents tested. Hence, there is no need to dry the biomass to well before processing. However, addition of water increases the operating pressure significantly.. •. For guaiacol, the rate of wood liquefaction appeared to proceed by a first-order reaction in wood with an apparent activation energy of 101 kJ mol-1 and a preexponential factor of 1.18*106 s-1.. •. Attempts to recycle the bio-crude through refill experiments showed high biocrude yields with a reduced oxygen content and low solid yields. However, successive refills led to a rapid build-up of heavy products and an increase in.

(60) liquefaction process that uses the product bio-crude as the liquefaction medium after the removal of the light and heavy products. However, further improvements are still required, particularly to reduce the formation of heavy products or to remove them from the recycled bio-crude via either physical separation or chemical conversion.. Chapter 3: Solvent, process parameter and recycle bio-crude screening. Based on these findings, we propose a simple, small-scale and decentralized. |. product prior to recycling seems to be required.. 51. the viscosity of the liquid. Hence, further reduction or withdrawal of the heavy.

(61) 4. References 1.. Kleinert, M. and Barth, T., Towards a Lignincellulosic Biorefinery: Direct One-Step Conversion of Lignin to Hydrogen-Enriched Biofuel. Energy & Fuels, 2008. 22(2): p. 13711379.. 2.. Knežević, D., van Swaaij, W., and Kersten, S., Hydrothermal Conversion Of Biomass. II. Conversion Of Wood, Pyrolysis Oil, And Glucose In Hot Compressed Water. Industrial & Engineering Chemistry Research, 2009. 49(1): p. 104-112.. 3.. Czernik, S. and Bridgwater, A.V., Overview of Applications of Biomass Fast Pyrolysis Oil. Energy & Fuels, 2004. 18(2): p. 590-598.. 4.. Behrendt, F., Neubauer, Y., Oevermann, M., Wilmes, B., and Zobel, N., Direct Liquefaction of Biomass. Chemical Engineering & Technology, 2008. 31(5): p. 667-677.. 5.. Elliott, D.C., Beckman, D., Bridgwater, A.V., Diebold, J.P., Gevert, S.B., and Solantausta, Y., Developments in direct thermochemical liquefaction of biomass: 1983-1990. Energy & Fuels, 1991. 5(3): p. 399-410.. 52. 6.. Stevens, J., Young, M., Euhus, D., Coulthard, A., Naae, D., Spilker, K., Hicks, J.,. |. Bhattacharya, S., and Spindler, P., Solvent-Enhanced Biomass Liquefaction. 2012, Catchlight. Chapter 3: Solvent, process parameter and recycle bio-crude screening. Energy LLC. 7.. Castellvi Barnes, M., Kersten, S.R.A., Lange, J.-P., and Zhao, W., Process for Conversion of a Cellulosic Material 2013, Shell Internationale Research Maatschappij B.V.. 8.. Mishra, G. and Saka, S., Kinetic behavior of liquefaction of Japanese beech in subcritical phenol. Bioresource Technology, 2011. 102(23): p. 10946-10950.. 9.. Maldas, D. and Shiraishi, N., Liquefaction of biomass in the presence of phenol and H2O using alkalies and salts as the catalyst. Biomass and Bioenergy, 1997. 12(4): p. 273-279.. 10.. Mun, S.P. and Hassan, E.M., Liquefaction of Lignocellulosic Biomass with Mixtures of Ethanol and Small Amounts of Phenol in the Presence of Methanesulfonic Acid Catalyst. Journal of Industrial and Engineering Chemistry, 2004. 10(5).. 11.. Mun, S.P. and Hassan, E.M., Liquefaction of Lignocellulosic Biomass with Dioxane/Polar Solvent Mixtures in the Presence of an Acid Catalyst. Journal of Industrial and Engineering Chemistry, 2004. 10(3): p. 473-477..

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